It is known to form a cross-sectional profile of a tubular member by a hydro-forming process in which a fluid filled tubular blank is placed within a cavity of a die and then the die is closed so that the tubular blank is pinched within the die. Fluid pressure is then increased inside the tubular member to expand the blank outwardly against the cavity of the die to provide a tubular product having a die formed cross-sectional profile.
It is also known that hydroformed components are formed from ductile materials in sheet or tubular form by exerting fluid pressure to push the component material against the part defining surfaces of the cavity of the die. In the case of tubular hydroforming, in which the tube may be either rolled and welded, seamless, or extruded, the fluid that causes pressure forming is introduced through seals located at axial ends of the tube. The seals may either be of a type that lock the ends of the tube in their starting position, seal in such a way that allows some forming inducing motion of the end of the tube, or makes contact with the end of the tube to create a contact end seal. The last mentioned seal is often used to feed material into the die to enhance formability by inducing axial stress and changing the strain path of the formed material.
Axial feeding is used to enhance the ability to produce forms having a perimeter substantially larger than a starting perimeter of the tube. The typical process of hydroforming a component with axial feeding is to concurrently control the axial feeding and the internal pressure so that the die is substantially filled with material at the lowest pressure that is compatible with controlling material folding and wrinkling. During axial feeding, the seals are moved or driven into the tube axially. After achieving substantial die filling, the pressure is raised, without additional axial feeding of the seals in order to complete forming detail features of the part. In some cases, the hydroformed component produced may experience thinning or thickening as a result of various influences of part shape, e.g. part expansion, or material flow re-direction at, for example, the base of an extrudate when forming a “T” fitting, or at locations opposite the extrudate in a “T” fitting.
As a result, it is desirable to provide a new method of forming a thickened tubular member. It is also desirable to provide a method of forming a thickened tubular member by axial feeding. It is further desirable to provide a method of forming a tubular member with thickened axial ends that would allow welding of the hydroformed component in a weldable range or in a more robust welding condition. Therefore, there is a need in the art to provide a method of forming a thickened tubular member that meets these desires.